1. Field of the Invention
The present invention relates to a dielectric film manufacturing method.
2. Description of the Related Art
In the development of a semiconductor device which has been making progress in higher element integration, the reduction of an operating voltage is being achieved along with the progress of element miniaturization in each element. For example, in the field of a MONOS (Metal Oxide Nitride Oxide Semiconductor) type nonvolatile semiconductor device, a blocking film, which separates a charge preserving layer (charge trap layer) and a gate electrode, is required to have a higher permittivity along with the element miniaturization. Similarly, in the field of a FG (Floating Gate) type nonvolatile semiconductor device, an insulating film between a floating electrode and a gate electrode is required to have a higher permittivity along with the element miniaturization. The charge trap layer of the MONOS type device is formed with a silicon nitride film, for example, and is required to have a high relative permittivity and also a low leak current and further required to have a large band gap against the silicon nitride film, as the blocking film. A technique utilizing Al2O3 as such a blocking film is being discussed. A method of forming the Al2O3 film includes a CVD (Chemical Vapor Deposition) method, an atomic-layer adsorption deposition method (ALD), and a sputtering method. The CVD method has an incubation time in the formation process and thus has problems of film thickness controllability, surface uniformity, and reproducibility. Meanwhile, the sputtering method has a problem of plasma damage and a problem of interface layer formation caused by oxidation of a substrate to be processed.
As a formation method of an Al2O3 film by the ALD method or the CVD method, a technique forming an Al2O3 film containing α-Al2O3 by the use of aluminum chloride (AlCl3) and oxidation gas is disclosed in Japanese Patent Application Laid-Open Publication No. 2009-105087. This technique has an advantage of obtaining a film having a large band gap of 8.8 eV.
Further, Extended Abstracts of the 2009 International Conference on Solid State Devices and Materials, 2009, pp. 156-157 describes that element reliability is improved by the use of Si-rich AlSiOx having an amorphous structure as the blocking film.
Further, as a method for forming a dielectric film having a high dielectric constant by sputtering, Japanese Patent Application Laid-Open Publication No. 2000-129445 discloses a technique utilizing crystalline metal oxide containing Al and Si as an abrasion resistant film.
In the above techniques, however, there are respective problems as follows.
In the technique of forming an Al2O3 film containing α-Al2O3 by using oxidation gas including aluminum chloride (AlCl3) and water vapor, which is disclosed by Japanese Patent Application Laid-Open Publication No. 2009-105087, an α-Al2O3 film having a large band gap is obtained, but a gas including chloride (Al Cl3) as a source gas and water vapor as an oxidation gas are used, respectively, and thus there arises a problem of erosion of the inside of a semiconductor production apparatus caused by hydrogen chloride formation. Further, when a silica reaction tube is used as a component of a semiconductor production apparatus, there arises a problem that the silica reaction tube is eroded by the aluminum chloride.
The technique of utilizing Si-rich AlSiOx having an amorphous structure as the blocking film, which is disclosed in Extended Abstracts of the 2009 International Conference on Solid State Devices and Materials, 2009, pp. 156-157, can suppress a leak current via a crystal grain boundary by making the blocking film amorphous, but relative permittivity is reduced in comparison with the Al2O3 film including a crystalline phase and thus there arises a problem that it is difficult to make the blocking film thinner. Further, there is a problem that the most preferable Si content rate is not disclosed.
Further, the crystalline metal oxide containing Al and Si, which is disclosed in Japanese Patent Laid-Open No. 2000-129445, is described to be able to form the crystalline phase of α-Al2O3 having an excellent abrasion resistance, but, although it is required, in the application to semiconductor element manufacturing, to form a uniform alumina film on a semiconductor wafer surface, a technique to solve such a problem is not disclosed in Japanese Patent Application Laid-Open Publication No. 2000-129445 and it is difficult to apply this technique to the semiconductor element manufacturing.